Method of Printing

ABSTRACT

The invention provides a method of printing a textile comprising polyester, or a full-chrome, semi-chrome or vegetable-tanned leather, with a vat or a sulfur dye, comprising inkjet printing a solubilised vat dye or a solubilised sulfur dye onto the textile or the leather.

FIELD

The present invention relates to a method of printing, in particular a method of printing with solubilised vat and solubilised sulfur dyes, onto textiles, such as polyester and polyester-containing textiles, as well as related substrates such as certain types of leather. In particular the invention provides a method of inkjet printing of solubilised vat and solubilised sulfur dyes on to textiles as well as related substrates.

BACKGROUND

Inkjet printing technology, e.g. digital inkjet printing technology, is becoming increasingly important industrially for textile coloration, attracting growing interest from print technologists and designers, especially in view of its potential to provide high production flexibility and responsiveness (H Ujiie, Digital printing of textiles, Woodhead Publishing, Cambridge (UK), 2006). The technology also has distinct attractions from an environmental perspective. Printing ink formulation technology is now well-established commercially and generally involves use of dye classes based on the fibre type. For example, acid dyes are normally used for protein fibres and disperse dyes for polyester. Inkjet printing of cellulosic fibres, including cotton, viscose and lyocell, most commonly uses specifically selected reactive dyes (see for example S O Aston et al. (Jet printing with reactive dyes, JSDC, 1993, Vol. 109, 147-152); M Kanik and P J Hauser (Printing of cationised cotton with reactive dyes, Coloration Technology, 2002, Vol. 118, 300-306); and A W Kaimouz (R H Wardman and R M Christie, The inkjet printing process for lyocell and cotton fibres, part 1: The significance of pre-treatment chemicals and their relationship with colour strength, absorbed dye fixation and ink penetration, Dyes and Pigments, 2010, Vol. 84, 79-87)).

Cellulosic fibres are also commonly dyed or screen printed with vat dyes, especially for high performance applications, since they can offer superior performance to reactive dyes in terms of lightfastness and ability to tolerate more aggressive laundering procedures. Also, in application, they consume less water for washing and clearing. Vat dyes have thus successfully maintained their position for high quality dyed and printed cellulosic textiles, for example in curtains and upholstery (U Baumgarte, Vat dyes and their application, Rev. Prog. Coloration, 1974, Vol. 5, 17-32).

Sulfur dyes, which show some similarities to vat dyes in application methodology, can be applied to cellulosic fibres in certain cases, to give high washfastness and reasonable lightfastness.

There is considerable interest in the development of methodology to deliver vat dyes and sulfur dyes onto textiles using digital inkjet technology. However, inkjet printing with these dyes remains problematic, because of their pigmentary nature and also because of the aggressive chemical processing generally required for their application.

A generalised scheme for the chemistry involved in vat dyeing is depicted in Scheme 1 below:

Vat dyes were originally developed in medieval Europe and are now a well-understood class of a variety of water-insoluble dyes. The insoluble, coloured form of the vat dye depicted schematically (top) in Scheme 1 is subjected to reduction, generally using sodium dithionite under alkaline conditions (e.g. using NaoH). This provides the water-soluble leuco form which is substantive and capable of penetration into cellulosic fibres. Oxidation (e.g. using H₂O₂) regenerates the pigmentary form within the fibre. Mechanical entrapment of individual crystallites serves to provide excellent fastness properties.

It will be understood by those skilled in the art that the conjugated system of double bonds depicted between the two carbonyl groups depicted in the insoluble form shown in Scheme 1 serves simply to represent schematically the structure of a typical insoluble vat dye. Structural variations on this schematic will be immediately evident to the skilled person, for example, the presence of a single carbon-carbon double bond between the carbonyl groups in the archetypal vat dye indigo, or a polycyclic aromatic system as in the vat dye indanthrene golden yellow. Similarly, of course, vat dyes need not necessarily have exactly two carbonyl groups.

Sulfur dyes are water-insoluble dyes, often with indeterminate structure which contain sulfur atoms as an integral part of the chromophore as sulfide and polysufide links often built in to heterocyclic structures. Usually, sulfur dyes are applied in an alkaline medium containing sodium sulfide solution to form a soluble reduced (leuco) form which is subsequently oxidised to the insoluble form in the fibre. Their application is thus closely analogous to vat dyes.

One potential approach to inkjet delivery of vat or sulfur dyes is to print the dyes in the form of finely-dispersed pigments, followed by the required reduction/oxidation fixation process, carried out either using fabric pre-treatment or post-treatment processing. Alternatively, a process may be envisaged whereby the water-soluble leuco form of the vat or sulfur dye is delivered by inkjet. However, the former process is disadvantageous in requiring delivery of particulate matter, with an inevitable possibility of blockage at the print head; the latter is disadvantageous by exposing the print head to the aggressive alkaline reduction medium used, and would also present significant difficulties with ink stability because of the ease of air oxidation of the leuco dye solutions.

In the prior art, solubilised vat and solubilised sulfur dyes have been described in EP 274216 A as suitable for use in inkjet ink formulations. This publication describes an ink comprising a water-soluble dye and an antioxidant, the dye being oxidizable to the water-insoluble form; and a process for inkjet recording on a recording medium, upon which the ink may then be fixed by printing. Whilst there is mention made of the recording medium being cloth, the focus in this publication is on the recording medium being paper, specifically “not only designated paper specially prepared for use in ink-jet recording but also other recording media having a recording face on which fibres are exposed, in particular generally used ordinary sized paper typified by copying paper, report paper, bond paper and continuous business form.

GB 2169242 A describes a method for aqueous jet-ink printing on textiles pre-treated with a polymeric acceptor. The patent describes that any known dye can be used, but describes as preferable that selection of the dye is based upon the nature of the fibres constituting the cloth on which printing is to be effected. Thus, for example, the application suggests use of disperse dyes as a dye for the ink where the cloth comprises synthetic and/or semi-synthetic fibres as the main component; or use of disperse dyes as one dye component for the ink where the cloth is a mix-spun fabric.

SUMMARY

We have surprisingly found that inkjet printing is a suitable technology with which to assist incorporation of vat and sulfur dyes into textiles, in particular polyester or polyester-containing textiles, and other related substrates. This may be achieved by a process of printing in which a solubilised vat or sulfur dye is inkjet-printed onto a textile substrate or other related substrate, such as certain leathers. The invention is of benefit to the art of printing, in the light of the combined technical benefits of (i) vat and sulfur dyes and (ii) inkjet printing and is a particularly surprising finding given the description of the application of inkjet printing of solubilised vat dyes on to paper in patent applications filed more than twenty years ago and the phenomenal advances in inkjet printing technology over the same period.

Viewed from one aspect, therefore, the invention provides a method of printing a textile comprising polyester, or a full-chrome, semi-chrome or vegetable-tanned leather, with a vat or a sulfur dye, comprising inkjet printing a solubilised vat dye or a solubilised sulfur dye onto the textile or the leather.

Viewed from a second aspect, the invention provides the use of a solubilised vat dye or a solubilised sulfur dye as a means of providing colour on a textile comprising polyester, or a full-chrome, semi-chrome or vegetable-tanned leather, the use comprising a method of inkjet printing the solubilised vat dye onto the textile or the leather.

Viewed from a third aspect, the invention provides a textile obtainable according to the first or second aspect of the invention.

Further aspects and embodiments of the present invention will be evident from the discussion that follows below:

DETAILED DESCRIPTION

The present invention arises, in part, from the recognition of the utility of inkjet printing in incorporating vat or sulfur dyes into polyester-containing textiles, which despite the technical advantages of both this method of printing and the dye classes, and the desirability of being able to effect inkjet printing of these classes of dyes onto polyester-containing textiles, with its inherent precision and high resolution not achievable with more traditional non-digital textile printing processes such as screen printing, for example, has not been described hitherto.

The invention provides for printing onto textiles. By textile is meant herein a woven or knitted fabric, that is to say a fabric with interlacing fibres resultant from weaving, knotting, crocheting or knitting together natural or artificial fibres. The fibres may be, and typically are, in the form of thread, i.e. a fine strand made by drawing out and twisting fibres; or a yarn, i.e. a long strand produced by spinning fibres. As is known in the art, textiles are distinguished by virtue of their method of manufacture from other another class of substrates: non-woven fabrics, which are also made of fibrous material, are manufactured fabrics in which production is through bonding achieved by application of heat, mechanical pressure or chemical (including solvent) treatment.

An example of a non-woven fabric is felt: felting involves consolidation by heat and mechanical action to matt fibres together. Paper is another example of a non-woven fabric, since it is produced by pressing together fibres typically derived from wood pulp or other fibrous material and drying.

According to particular embodiments of the invention the textile to which the solubilised vat dye and/or the solubilised sulfur dye is applied, i.e. printed, is a polyester textile or a textile formed from a blend of polyester and another fibre, e.g. a cellulosic fibre such as cotton. These embodiments of the invention—application of solubilised vat dyes or solubilised sulfur dyes onto textiles comprising, consisting of or consisting essentially of polyester—are of particular note given that polyester fabrics are almost universally dyed using disperse dyes. This is because of the general prejudice in the art against printing polyester materials, including the polyester component within polyester/cotton (often known as “polycotton”) blends, with vat or sulfur dyes, solubilised or otherwise. For example, and as described by U Baumgarte (infra), polyester-cellulosic fibre blends are typically treated with different dyes for the different components within the material, for example application of a disperse dye for the polyester component and a vat, sulfur, reactive or direct dye for the cellulosic, e.g. cotton, component. U Baumgarte describes the use of mixtures of vat and direct dyes as having become established in Europe.

Where the textile comprises a non-polyester component, this component may comprise, consist or consist essentially of natural or synthetic fibres, or may comprise a mixture of natural and synthetic material, e.g. fibres. For example, the component may comprise, consist of or consist essentially of a cellulosic-based material, such as cotton, viscose or lyocell or other material, derived from plant materials such as wood or hemp, for example, or any mixture of the foregoing. Alternatively or additionally, the textile may comprise, consist of or consist essentially of a fibrous protein material, such as wool, cashmere, mohair or angora, or any mixture of the foregoing. Alternatively or additionally the component may comprise, consist of or consist essentially of an additional synthetic material such as a polyacrylonitrile, a polyamide or a polyolefin (e.g. polypropylene), or any mixture of the foregoing. Other related types of substrates to which this invention may be applied include certain types of leather, including full-chrome, semi-chrome and vegetable tanned leathers.

According to particular embodiments of the present invention, that which is printed on is a textile which comprises a mixture of polyester and cotton. Typical mixtures, e.g. polycotton blends, comprise between about 90% cotton and 10% polyester to about 10% cotton and 90% polyester, for example between about 70% cotton and 30% polyester to about 30% cotton and 70% polyester.

As is known to those in the art, the term polyester defines the chemical nature of this class of polymers. However, the most common polyester, and which is used predominantly in the manufacture of textiles is poly(ethylene terephthalate) and so all references to polyester herein refer according to some embodiments to this particular polyester.

Provided according to particular embodiments of the method according to the first aspect of the invention, therefore, are methods comprising printing a formulation consisting essentially of the solubilised vat dye and/or a solubilised sulfur dye. By this is meant that the coloring means in the formulation consists essentially of a solubilised vat dye and/or a solubilised sulfur dye. Thus, according to these embodiments, other colouring components may be present, which do not materially affect the fundamental and novel characteristics of these embodiments of the invention. To use alternative words additional components may be present only if the essential characteristics of the resultant formulation are not materially affected by the presence of such components. Thus, according to these embodiments, the presence of other dyes, in particular disperse dyes, or pigmentary material in such formulations is substantially excluded, since the fundamental and novel characteristics of these embodiments of the invention relate, for example, to the use of the method in colour-printing, with a dye, a polyester textile (or textile consisting essentially of polyester), or the polyester component within a textile made from mixed fibres.

Provided according to other particular embodiments of the method according to the first aspect of the invention are methods comprising printing a formulation consisting of a solubilised vat dye and/or a solubilised sulfur dye as the coloring means in the formulation Provided according to still further particular embodiments of the method according to the first aspect of the invention absent dyes other than vat dyes and/or sulfur dyes, e.g. absent dyes other than vat dyes.

Analogously, there are provided according to particular embodiments of the use according to the second aspect of the invention, uses according to which solubilised vat dyes or solubilised sulfur dyes are used as a means of providing colour on the textile, if this is a polyester textile (or textile consisting essentially of polyester), or a means of providing colour on the polyester component within a textile made from mixed fibres. In other words, the solubilised vat dye or the solubilised sulfur dye is used as a means of providing colour on polyester.

Vat dyes are a well-understood dye class, defined by virtue of the chemistry involved in their application, described briefly above, including with reference to Scheme 1.

Solubilised vat dyes are structurally related to leuco vat dyes. However, instead of the simple salt form (the leuco base) resultant from the reduction of the insoluble form under alkaline conditions, solubilised vat dyes, as is well-understood to those of skill in the art of colouring, define an alternative class of reduced vat dyes containing a water-solubilising group, such as the salt, e.g. sodium salt, of a sulfate ester, shown structurally in formula (I) below):

Solubilised vat dyes are widely available commercially, e.g. from Karan Dyestuffs, Ltd, Jagson Colorchem Limited and others and need not be discussed in detail here. A wide variety of colours and structural subclasses of vat dyes, for example solubilised anthraquinonoid, acylamino-anthraquinone, anthrimide, indanthrone, flavanthrone and carbazole vat dyes, are available in solubilised form.

Particular examples, not intended to limit the scope of the invention, include C.I. Solubilised Vat Green 1, 2, 3, 4, 21, 30; C.I. Solubilised Vat Blue 1, 2, 3, 4, 5, 6, 7, 8, 9, 41, 73; C.I. Solubilised Vat Brown 1, 3, 5, 6, 7, 38; C.I. Solubilised Vat Red 1, 2, 3, 4, 6, 8, 9, 10, 11, 34, 45; C.I. Solubilised Vat Orange 1, 2, 3, 4, 5, 6, 9, 11; C.I. Solubilised Vat Black 1, 2, 4, 5, 6, 8, 25, 6; C.I. Solubilised Vat Violet 1, 2, 3, 4, 5, 6, 7, 8; and C.I. Solubilised Vat Yellow 1, 2, 4, 5, 6, 7, 8, 45, 47;

Analogously, solubilised sulfur dyes are also well-understood by those of normal skill in the art. A solubilised sulfur dye is defined as ‘a thiosulfuric acid derivative of a sulfur dye which during dyeing or printing is converted into the substantive alkali-soluble thiol form’ (W. E. Dood, Review of the Progress in Coloration Technology, Vol. 7, 1976, page 80-84). A wide variety of solubilised sulfur dyes are available commercially. Examples, not intended to limit the scope of the invention, include: C.I. Solubilised Sulfur Green 1, 2, 3, 6, 9, 14, 19, 22, 25, 27, 31, 36, 37; C.I. Solubilised Sulfur Blue 2, 3, 5, 7, 9, 11, 13, 15, 19; C.I. Solubilised Sulfur Brown 1, 8, 10, 12, 15, 16, 21, 46, 51, 52, 63, 88, 89, 90, 91, 93, 96; C.I. Solubilised Sulfur Red 2, 6, 7, 10, 11, 12, 13; C.I. Solubilised Sulfur Orange 1; C.I. Solubilised Sulfur Black 1, 5, 6, 8, 11; and C.I. Solubilised Sulfur Yellow 9, 16, 19, 20;

It will be understood from the foregoing discussion that the application of solubilised vat or solubilised sulfur dyes via inkjet printing is advantageous because solubilisation of the reduced form of the dye is achieved not by virtue of alkaline environment of the acidic hydroxyl groups, when forming the leuco form, but by forming soluble esters, such as, and typically, sulfate esters of these hydroxyl groups, present in the so-called vat acid or leuco vat acid (i.e. the non-salt form of the reduced vat dye) or a thiosulfuric acid based ester derivative of a sulfur dye.

These reduced, solubilised vat or sulfur dyes may then be manipulated in solutions at pH values close to neutrality (e.g. at pH values between about 5 and about 9), and so formulations can be less damaging to inkjet equipment, in particular the nozzles through which the ink is jetted, than inks in which extremes of pH are used.

According to the invention a solubilised vat dye or a solubilised sulfur dye, or a combination of a solubilised vat dye or a solubilised sulfur dye, is printed by inkjet printing onto a textile or a leather. One or more solubilised vat dyes or solubilised sulfur dyes may be printed simultaneously and/or colour patterning achieved, particularly through the application of digital inkjet technology. All the technology by which this may be achieved is highly advanced and well-understood by those skilled in the art. For details of inkjet printing, reference may be made for example to The Chemistry of Inkjet Inks, Shlomo Magdassi, Ed., World Scientific Publishing Co. Pte Ltd, 2008, and references cited therein.

Whilst the formulation of inkjet inks is a well-understood technique by the skilled person (see again The Chemistry of Inkjet Inks, infra) and can be achieved without undue burden, it is appropriate to describe some particular features of inkjet formulation useful according to this invention, which arise from the incorporation of solubilised vat or solubilised sulfur dyes in contrast to other dye classes such as acid, disperse and reactive dyes.

Formulations are desirably prepared from dyes of high purity, particularly with respect of minimising inorganic salts and reducing as much as possible (and preferably excluding) particulate matter, considerations that are not so important where vat or sulfur dyes (or the corresponding solubilised dyes) are used in dyeing processes (i.e. colouring of an entire fabric, in contradistinction to printing processes) or even other printing methods such as screen printing.

Appropriate purification of commercially available solubilised vat or sulfur dyes is readily achievable, e.g. through purification processes involving, one or more recrystallisations with filtration of residual solids at appropriate stages as appropriate, or by processes using ultrafiltration or reverse osmosis.

Of particular importance to solubilised vat and solubilised sulfur dyes in formulations intended for printing via inkjet is the advantageousness of avoiding, as much as is practicable, precipitation of the vat dye or sulfur dye in advance of its application to the textile, which arises from premature hydrolysis/oxidation of the dye. Such precipitation can give rise to undesirable agglomeration of resultant particulates of vat or sulfur dye, and possible clogging of the nozzles of the inkjet printhead.

The examples below provide some non-limiting examples of how to avoid the premature precipitation of vat or sulfur dyes when a solubilised vat or solubilised sulfur dye is used as a colorant in the inkjet inks. Thus, according to some embodiments of the invention, an appropriate antioxidant or combination of antioxidants is incorporated into the ink, although it is important to ensure that the antioxidant or combination of antioxidants is compatible when used in combination with the other constituents used during the inkjet ink formulation, such as humectants and viscosity modifiers. These may be selected, with routine skill, so as to compromise satisfactorily the conflicting demands for formulations to have a useful shelf life and the need for oxidation of the solubilised vat acid or solubilised sulfur dye to take place after application to the fabric.

Suitable antioxidants may be selected by the skilled person, for example a hydroquinone or ascorbic acid. Others will be evident to those of normal skill in the art.

According to some embodiments of the present invention highly effective water-based inkjet ink formulations may be used, with a significant concentration of dye, typically between about 5 and about 10% wt/v (over 9% in selected cases), with satisfactory physical and rheological characteristics giving good jettability, prolonged storage stability (over 6 months) and adequate colour strength development on the printed fabrics.

After printing of the substrate with solubilised vat or sulfur dye based inkjet inks, the printed substrate is generally subjected to a controlled treatment (post-treatment) to produce the coloured insoluble and oxidised form of the vat and/or sulfur dye on and within it. This may be achieved in a number of ways including thermal treatment (involving hydrolysis and air oxidation), aqueous chemical oxidation and photo-oxidation by UV irradiation. This oxidation can be a single operation or a combination of a series of operations with controlled conditions such as time, temperature, concentrations of reagents, etc. For example, the printed textile may be subjected to a thermal treatment at a temperature of between about 100 and about 200° C., for example between about 120 and about 150° C. for a period of between about 2 and about 90 minutes, e.g. between about 5 and about 45 minutes in steam or in a hot air, for example in an oven with hot air. Such thermal treatments are a highly effective first stage of the post-treatment. Without wishing to be bound by theory, it is our belief that this to causes penetration of the solubilised form of the dye into the textile and also initiates the hydrolysis process leading to the leuco form of the dye, which may well be substantially in its leuco acid (protonated form) followed by oxidation, i.e. conversion to the insoluble vat or sulfur dye.

An aqueous oxidation process advantageously follows the thermal treatment to effect complete conversion to the insoluble using a nitrite salt of an alkali metal, e.g. sodium, and a mineral acid, preferably sulfuric acid. This general method, well known to the skilled person was found to be suitable for inkjet printed substrates, e.g. textiles, and more efficient than using methods based on hydrogen peroxide. However, we have also found that UV-initiated photooxidation using UV lamps operating in the UVA and UVB wavelength regions may be used to effect the desired oxidation, offering particular advantages for inkjet printing in that the use of a final wet oxidation process may be avoided.

It is a surprising and important feature of this invention that inkjet prints containing vat dyes and sulfur dyes with good colour depth, excellent fastness to light, washing, rubbing, sublimation and perspiration may be achieved where the substrate is a polyester-containing textile. Again, without wishing to be bound by theory, we believe that the thermal post-treatment assists in initiating generation of the acid form of the dye, a neutral molecule, which penetrates polyester or polyester-containing fibres by a similar mechanism to that of disperse dyes. The acid form of the dye is then fixed by oxidation to the vat (or sulfur) dye form, causing mechanically entrapment as individual crystallites. It is thus of particular significance that cotton/polyester blends, which constitute a very high proportion of textile fabrics in current use, or other cellulosic/polyester fabric blends, can be printed in a simple process using a single dye class, as an alternative to the current process which commonly involves separate applications of reactive dyes (for cellulosic fibres) and disperse dyes (for polyester fibres) with very different application conditions required for the different processes.

Variations on the foregoing method of effecting the final oxidation, and optionally preceding hydrolysis step, are also known to the skilled person. Thus, for example, alternative oxidants may be used, such as other alkali metal nitrites, or alkali metal, e.g. sodium, chromates, perborates, persulfates or chlorates, or mixtures of these. The acid may be varied by, e.g. employing other mineral acids such as phosphoric or hydrochloric, or carboxylic acids such as acetic formic, tartaric or oxalic, or mixtures of these. Alternatively, salts, e.g. ammonium salts, of any of the foregoing acids or mixtures of these, and which serve to provide an acid upon heating, may be used.

As a still further alternative is the possibility known in the art (see UK patent publication no. 1,203,324) of omitting an acid and effecting fixation and precipitation of the dye by treating the inkjet-printed textile with an aqueous solution of alkali metal nitrite, e.g. sodium nitrite, or other suitable oxidant (including those listed hereinbefore), and subjecting the thus-treated, and subsequently dried, printed textile to a brief thermal treatment at elevated temperature (e.g. for a period of time from 5 seconds to 5 minutes at a temperature of 140° C. to 200° C.). Heating may be achieved through application of hot air, contact with heated rollers or application of infrared beams.

Formulations of solubilised vat and solubilised sulfur dyes are readily achievable. Typically these will be water-based. Water-based and other inkjet inks may be readily formulated to provide the appropriate physical, rheological behaviours for high quality inkjet inks. Typical components of the formulation are: humectants, including but not limited to ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, thiodiglycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerol, mesoerythritol, pentaerythritol, trimethylolethane, trimethylolpropane, 1,4-cyclohexanediol, 1,4-cyclohexane dimethanol, cyclohexanethiol, triethyleneglycolmonobutylether, diethyleneglycolisobutyl ether, diethyleneglycolmonoethylether, triacetin, N-methyl-2-pyrrolidone, urea, thiourea, ethylene urea, alkyl urea, alkyl thiourea, dialkylurea, diols, glycols, and the like; solvents, including but not limited to, alcohols, aromatic hydrocarbons, ketones, esters, aliphatic hydrocarbons, higher fatty acids, carbitols, cellosolves, glycol ethers, and the like; viscosity modifiers, including but not limited to, water-soluble polymers, such as polysaccharides (e.g. a hydroxyethylcellulose, a carboxymethylcellulose, hydroxypropylcellulose), chitin and its derivatives, chitosan and its derivatives, starch, carrageenan, polyvinyl alcohol, polyethylene oxide, proteins, polystyrenesulfonic acid, etc., water-dispersible polymers, such as polyvinylacetate, polyhydroxyethylacetate, polyvinylpyrrolidone, cyclodextrin and the like; surface tension modifiers, such as, surfactants, wetting agents or dispersing agents suitable for aqueous inkjet inks, biocides, such as biocides which are usually used for aqueous inkjet inks, such as, sodium dihydroacetate, 2-phenoxyethanol, sodium benzoate, sodium pyridinethion-1-oxide, ethyl p-hydroxybenzoate and the like; and other components customarily included in aqueous inkjet inks, such as buffering agents, moisture holding agents, dissolution aids, permeation controlling agents, antioxidants, antifungal agents, corrosion inhibitor and chelating agents.

It is well-known to those skilled in the art that for optimised image quality, textiles may be subjected to pre-treatments (i.e. prior to printing) with agents such as migration inhibitors, certain polymers, chitosan, chitin and the like; also with penetrating agents such as urea, thiourea, alkyl ureas and the like.

In conclusion, it is possible through this invention to provide ink-jet printed substrates, in particular textiles comprising polyester fibres. The invention allows application of the CMYK system (cyan, magenta, yellow, and key black) commonly used to produce multicoloured images on textiles and related substrates. Through this invention, it is possible to apply the precision of inkjet printing, particularly with digital control, to allow the application of vat dyes or sulfur dyes to substrates, particularly polyester-containing textiles.

Each patent and non-patent reference mentioned herein is hereby incorporated by reference in its entirety, as if the entire contents of each of these references were set forth herein.

The invention is illustrated by the non-limiting examples that follow below:

Materials

Solubilised Vat Yellow 4, Green 1, Blue 5, Red 1, Brown 5 and Black 16 were obtained from Karan Dyestuffs Ltd, India.

Equipment

A Xenjet 4000 inkjet dispenser system was used with a Xaar Omnidot 760 piezoelectric drop-on-demand print head, integrated with a syringe vacuum system connected to a Xaar ink supply controller, XUSB drive electronic box and print table. Viscosity and surface tension were adjusted during the ink formulation according to the print head requirements. Viscosity was measured using a Brookfield DV-II Viscometer and surface tension using a Kruss tensiometer, model K6.

EXAMPLE 1 Inkjet Ink Based on C.I. Solubilised Vat Green 1

Purified C.I. Solubilised Vat Green 1 (2 parts) was mixed with de-ionised water (80 parts) by stirring with a magnetic stirrer for 10 min to give a greenish-red solution. To this mixture was added formamidinesulfinic acid (8 parts) and 1,4-diazabicyclo(2,2,2)octane (5 parts) and the mixture was stirred for a further 60 min which produced a dark red solution. To this solution, triethyleneglycolmonobutyl ether (10 parts) and glycerol (10 parts) were added and the mixture stirred for an additional 3 hours. This solution was filtered twice using Whatman GF/F (Glass fibre based filter paper with retention 0.73 μm) to give a dark red inkjet ink with the following physical characteristics: pH 7.20, surface tension 35.5 dyn/cm, viscosity 1.94 cP (at rpm 60 and temperature 22.0° C.). This ink was used for inkjet printing using a piezoelectric printhead (Omnidot 760 GS8 printhead attached to a Xenjet 4000 series dispenser system, Xaar plc, UK). After printing, the printed textile was subjected to a thermal treatment (20 min at 150° C.) in a fan assisted oven followed by oxidation with an acidic hydrogen peroxide solution (acetic acid: hydrogen peroxide: de-ionised water in the ratio 3:6:1000) for 25 minute at 50° C. The process was then finished using a soaping, washing and drying procedure typical of vat dyed fabric. This ink showed good storage stability at room temperature. It showed good jettability during printing on to polyester, cotton/polyester blend and cotton fabrics, and gave high quality green printed images with good technical performance, such as excellent light and washfastness properties.

EXAMPLE 2 Inkjet Ink Based on C.I. Solubilised Vat Red 1

Bruggolit E01 Pulver (Methanesulfinic acid hydroxyl monosodium salt, Bruggemann Chemical Heilbronn, Germany) (8 parts), triethanolamine (5 parts) and Surfynol 465 (0.001 parts) were mixed with de-ionised water (170 parts) with stirring for 30 min to give a clear solution. Purified C.I. Solubilised Vat Red 1 (2 parts) was dissolved in this solution by stirring for a further hour. Then, glycerol (15 parts) and triethyleneglycolmonobutylether (5 parts) were added to this solution which was stirred for another one hour to give a colourless solution. This solution was filtered twice through a Whatman GF/F glass fibre based filter and the resulting ink showed the following physical characteristics: pH 8.25, surface tension 38.5 dyn/cm and viscosity 2.43 cP (at rpm 60 and temperature 21.5° C.). This ink was used for inkjet printing using a piezoelectric printhead (Omnidot 760 GS8 printhead attached to a Xenjet 4000 series dispenser system). After printing, the printed textile was given a thermal treatment (15 min at 150° C.) in a fan assisted oven followed by oxidation using a solution of sodium nitrite: concentrated sulphuric acid: deionised water (1:4:1000) for 1 hour at room temperature, and then finished using a soaping, washing and drying procedure typical of vat dyed fabric. This ink showed good storage stability at room temperature. It also showed excellent jettability during printing on to polyester, cotton/polyester blend and cotton fabrics, and gave high quality red printed images with good technical performance, such as excellent light and washfastness properties.

EXAMPLE 3 Inkjet Ink Based on C.I. Solubilised Vat Yellow 4

Methanesulfinic acid, hydroxy monosodium salt (4 parts), triethanolamine (2.5 parts), Dowicil 150 (0.0001 parts) and sodium dodecylbenzenesulfonate (0.0001 parts) were mixed with de-ionised water (80 parts) by stirring with a magnetic stirrer for 40 min to give a clear solution. Purified C.I. Solubilised Vat Yellow 4 (2 parts) was dissolved in this solution which was stirred for an hour with a magnetic stirrer at room temperature to give a transparent yellow coloured solution. To this solution diethyleneglycol (3 parts), triethyleneglycolmonobutylether (3 parts) and glycerol (9 parts) were added slowly and the mixture stirred for another one hour. This solution was filtered twice using a Whatman GF/F glass fibre based filter to give a clear yellow coloured inkjet ink with the following physical characteristics: pH 7.92, surface tension 37.2 dyn/cm and viscosity 2.20 cP (at rpm 60 and temperature 20.5° C.). This ink was inkjet printed using the same printing system as given for the previous examples. After printing, the printed textile was given a thermal treatment (for 10 min at 170° C.) in a fan assisted oven followed by oxidation using a solution of acetic acid: hydrogen peroxide: deionised water (5:10:1000) at 40° C. followed by finishing using a soaping, washing and drying procedure typical of vat dyed fabric. This ink showed good storage stability at room temperature. It also showed excellent jettability during printing on to polyester, cotton/polyester blend and cotton fabrics, and gave high quality yellow printed images with excellent light and washfastness properties.

EXAMPLE 4 Inkjet Ink Based on C.I. Solubilised Vat Blue 5

Methanesulfinic acid, hydroxy monosodium salt (10 parts), triethanolamine (10 parts), polyoxyethylene sorbitan monoleate (3 parts) and carbonyldiamide (10 parts) were mixed with de-ionised water (100 parts) and the mixture stirred with a magnetic stirrer for 4 hours to give a very pale yellowish solution. To this solution, purified C.I. Solubilised Vat Blue 5 (10 parts) was added and dissolved by stirring with a magnetic stirrer at room temperature overnight to give a nearly colourless solution. Then, triethyleneglycolmonobutylether (1 part) and glycerol (19 parts) were added slowly and the mixture stirred for 3 hours to give a clear solution with a very pale yellowish tone. This solution was filtered several times using a Whatman GF/F glass fibre based filter to give a nearly colourless inkjet ink with the following physical characteristics: pH 8.26, surface tension 38.92 dyn/cm and viscosity 2.43 cP (at rpm 60 and temperature 21.4° C.). This ink was inkjet printed using the same printhead as given for the previous examples. After printing, the printed textile was given a steam fixation (for 2 min at 170° C.) followed by oxidation using a solution of sodium nitrite: concentrated sulphuric acid: deionised water (2:5:1000) for 25 min at room temperature followed by finishing using a soaping, washing and drying procedure typical of vat dyed fabric. This ink showed very good storage stability at room temperature. It also showed excellent jettability during printing on to polyester, cotton/polyester blend and cotton fabrics, and gave high quality deep blue printed images with excellent light and washfastness properties.

EXAMPLE 5 Inkjet Ink Based on C.I. Solubilised Vat Blue 5

Methanesulfinic acid, hydroxy monosodium (5 parts), triethanolamine (5 parts) and polyoxyethylene sorbitan monoleate (2 parts) and β-cyclodextrin (2 parts) were mixed with de-ionised water (100 parts) by stirring with a magnetic stirrer for 48 hours to give a yellowish translucent dispersion. Then, 2-propanol (35 parts) and N-methylpyrrolidone (25 parts) were mixed into the dispersion. To this, purified C.I. Solubilised Vat Blue 5 (2 parts), triethyleneglycolmonobutylether (2 parts) and glycerol (16 parts) were added and the mixture stirred with a magnetic stirrer at room temperature for a further 48 hours to give a yellowish stable dispersion. This dispersion was filtered several times using a Whatman GF/F glass fibre based filter to give a pale yellow coloured inkjet ink with the following physical characteristics: pH 7.21, surface tension 37.65 dyn/cm and viscosity 2.19 cP (at rpm 60 and temperature 21° C.). This ink was inkjet printed using the same printhead as given for the previous examples. After printing, the printed textile was given a thermal treatment (for 10 min at 150° C.) in a fan assisted oven followed by oxidation using a solution of sodium nitrite: sulphuric acid: deionised water (1:4:1000) for 10 min at room temperature and then finished by washing and drying. This ink was stable at room temperature for a specific time. It also showed excellent jettability during printing on to polyester, cotton/polyester blend and cotton fabrics, and gave very high quality blue printed images with very good technical performance, such as excellent light and washfastness properties.

EXAMPLE 6 Inkjet Ink Based on C.I. Solubilised Vat Black 16

Formamidinesulfinic acid (4 parts), polyvinylpyrrolidone (4 parts), Surfynol 465 (0.001 parts) and triethanolamine (2.5 parts) were dissolved in deionised-water (85 parts) by magnetic stirring for 2 hours at room temperature. C.I. Solubilised Vat Black 16 (1 part) and glycerol (20 parts) were added to this solution and stirring was continued overnight to give a dark greenish solution. This solution was filtered several times using a Whatman GF/F glass fibre based filter to give a dark inkjet ink with the following physical characteristics: pH 8.29, surface tension 38.5 dyn/cm, viscosity 4.01 cP (at rpm 60 and temperature 20.5° C.). After printing, the printed textile was given a thermal treatment (for 15 min at 150° C.) in a fan assisted oven followed by oxidation using a solution of sodium nitrite, concentrated sulphuric acid and deionised water (with a ratio of 1:4:1000) for 1 hour at room temperature and then finished using a soaping, washing and drying procedure typical of vat dyed fabric. This ink showed good storage stability at room temperature. It also showed excellent jettability during printing on to polyester, cotton/polyester blend and cotton fabrics, and gave good quality black printed images with a bluish tone. All the printed textiles showed good technical performance, such as excellent light and washfastness properties. In addition, this ink was also used for inkjet printing on white crust, semi-chrome crust and full chrome crust leather (of goat skin origin). After printing, all the printed leather samples were given a thermal treatment for 5 min at 90° C. All the printed leather showed a good quality black image and excellent technical performance, such as excellent washfastness and lightfastness properties.

EXAMPLE 7 Inkjet Ink Based on C.I. Solubilised Vat Brown 5

Formamidinesulfinic acid (4 parts), carboxymethylcellulose (4 parts), Surfynol 465 (0.001 parts) and triethanolamine (2.5 parts) were dissolved in deionised-water (85 parts) by magnetic stirring for 2 hours at room temperature. C.I. Solubilised Vat Brown 5 (1 part) and glycerol (20 parts) were added to this solution and stirring was continued overnight to give a dark brown solution. This solution was filtered several times using a Whatman GF/F glass fibre based filter to provide a dark inkjet ink with the following physical characteristics: pH 8.12, surface tension 38.0 dyn/cm, viscosity 3.91 cP (at rpm 60 and temperature 21° C.). After printing, the printed textile was subjected to a thermal treatment at 150° C. for 15 min and irradiated with UV light (366 nm) (40 W/cm focused Hg lamp) for 1 hour. This ink showed good storage stability at room temperature. It also showed excellent jettability during printing on to polyester, cotton/polyester blend and cotton fabrics, and gave good quality brown printed images with good technical performance, such as very good light and washfastness properties. 

1-15. (canceled)
 16. A method, comprising: ink jet printing a formulation comprising a solubilised dye onto a textile, wherein said solubilised dye is selected from at least one of the group consisting of a vat dye and a sulfur dye and wherein said textile is selected from at least one of the group consisting of polyester and leather.
 17. The method of claim 16, wherein said method further comprises subjecting said printed textile to a temperature of between about 100° C. and about 200° C. for between about 2 to about 90 minutes.
 18. The method of claim 16, wherein said method further comprises subjecting said printed textile to an oxidative process selected from at least one of the group consisting of an aqueous alkali metal nitrite, an acid, and ultraviolet light.
 19. The method of claim 16, wherein said textile comprises polyester.
 20. The method of claim 16, wherein said textile comprises leather.
 21. The method of claim 16, wherein said leather is selected from at least one of the group consisting of full-chrome leather, semi-chrome leather and vegetable-tanned leather.
 22. The method of claim 16, wherein said textile is a fabric comprising interlacing fibres.
 23. The method of claim 22, wherein said interlacing fibres are selected from at least one of the group consisting of woven, weaved, knotted, crocheted or knitted.
 24. The method of claim 22, wherein said fibres are selected from at least one of the group consisting of natural and artificial.
 25. The method of claim 16, wherein said textile consists of polyester.
 26. The method of claim 16, wherein said textile consists essentially of polyester.
 27. The method of claim 16, wherein said textile comprises a mixture of polyester and an additional material.
 28. The method of claim 27, wherein said additional material is selected from at least one of the group consisting of a natural material or synthetic material.
 29. The method of claim 27, wherein said additional material is a cellulosic material.
 30. The method of claim 29, wherein said cellulosic material is cotton.
 31. The method of claim 16, wherein said formulation consists essentially of said solubilised vat dye.
 32. The method of claim 16, wherein said formulation consists essentially of a solubilised sulfur dye.
 33. The method of claim 16, wherein said solubilised dye is a colouring means.
 34. The method of claim 16, wherein said formulation further comprises one or more antioxidant materials.
 35. A textile made in accordance with claim 16, wherein said textile is selected from at least one of the group consisting of a polyester and a leather, and a printed solubilised dye wherein said printed solubilised dye is selected from at least one of the group consisting of a vat dye and a sulfur dye. 